Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 121720
Area Forecast Discussion
National Weather Service Blacksburg VA
1220 PM EST Thu Jan 12 2017
A warm front across northern Virginia into the Maryland
Panhandle will continue to lift north of the region today. A new
cold front will approach the region from the west late tonight
into early Friday, then stall across northern North Carolina
Saturday before return north as a warm front late Saturday. This
later front will then oscillate north and south across the
region into early next week keeping an unsettled and wet weather
pattern in place.
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 400 AM EST Thursday...
A cold front will approach from the west tonight, then drift
south into the region Friday stalling across northern NC Friday
night, then is destined to oscillate about the region through
the weekend keeping an unsettled, wet pattern in place. More on
that scenario in the Short Term section below.
The rest of today should be a relatively dry and quiet day
weather wise across the region. The region is essentially in a
warm sector, unlike any recent weather patterns. Although there
will be lots of cloud cover, strong southwest flow aloft (a 60kt
southwest jet at 850mb just to our west/north), the presence of
the warm sector, and 850mb temperatures in the +10C to +12C
range will yield a very warm day, in fact about 20 degrees above
normal. Temperatures today should have no problem surging into
the 50s to lower 60s, especially given that some areas are
already in the 60s early this morning across the west. The
coldest locations should continue to be the eastern areas where
residual snow cover will temper warming, although much of the
snow cover disappeared Wednesday with the rain and temperatures
above freezing all day, so the effect of the snow cover may be
more limited than current thinking. MOS guidance from the
various models appeared too cold and was likely reflecting the
residual snow cover. Ended up using a blend of several models,
but even then had to raise readings a few degrees across the
Tonight will remain mild with the area remaining in the warm
sector ahead of the next front. Low temperature will only be in
the 40s and 50s. Contrast these readings with the below zero and
single digit temperatures that we in place just a few days ago.
Expecting very little precipitation today or tonight, although
some scattered light rain will drift into the far
western/southwestern areas late tonight/early Friday in advance
of the next front.
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.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 430 AM EST Thursday...
We will be in the southern stream of a split flow regime with a closed
low near the Baja peninsula and some flat ridging over the southeastern
US, through the ridge will amplify a bit as the low starts to open and
ejects off to the northeast. This pattern will produce wind flow
generally parallel to a baroclinic zone to our west and limit any
eastward progress. Strong surface high pressure moving through the
Great Lakes will wedge down east of the Appalachians and push backdoor
cold fronts through the region with cool and damp conditions and below
normal temperatures through the weekend. With a typical wedge
configuration expected, locations along the western periphery from the
Mountain Empire of VA into the northwest mountains of NC will see
The first wedge will start to push in during the afternoon on Friday
and will bring an abrupt end to our well above normal temperatures.
Isentropic lift over the top of the wedge will bring increasing chances
for precipitation into Friday night, and as the cold wedge continues to
build some freezing rain and possibly sleet is expected to develop from
Greenbrier WV through the Alleghany Highlands and down the Blue Ridge a
bit. While the depth of below freezing air in the wedge will be
shallow, it will be quite slow to moderate and the freezing rain will
gradually transition to plain rain through Saturday. Any glaze of ice
is expected to be less than one tenth inch and may trigger an advisory
if later model runs remain consistent. A wave will run along
the baroclinic zone and may disrupt the wedge a bit on Saturday
night, but another strong high will wedge in for Sunday and
Sunday night. At this time it looks like just a chance of cold
rain for everyone but temperatures trends will be monitored
.LONG TERM /MONDAY THROUGH WEDNESDAY/...
.AS OF 334 PM EST Wednesday...
Amplified southern stream to take shape into next week with 2-3 systems
moving from the desert SW northward/northeastward to the upper MS
Valley. Will still be on the cloudier side at times, but at the moment
Monday looks like the driest day with highs in the 50s. Will see
frontal boundary approach midweek with southwest flow increasing aloft
keeping temperatures well above normal. Will see some showers scattered
around Tuesday with better chance Wed-Wed night as the front tracks
west of the Appalachians.
.AVIATION /17Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --As of 1217 PM EST Thursday...
Warm front has lifted well north of the CWA into PA, leaving the
area in a warm sector. Current warm sector air mass will remain in
place until a backdoor front arrives late Friday into Saturday. The
warm sector air mass is largely void of the lower ceilings at this
time. Winds will increase this afternoon with a strong 850mb jet
traversing the region.
Overnight, as winds veer more to the WSW across eastern WV, expect
low clouds to potentially develop with ceilings dropping into the
MVFR range at KLWB, KBLF, and possibly KBCB as well.
Still expect VFR cigs further east across the Piedmont.
Medium to high confidence in cigs throughout the TAF valid period.
Medium to high confidence in vsbys throughout the TAF valid period.
Medium to high confidence in wind dir/spd throughout the TAF valid
Extended Aviation Discussion...
Should see mainly sub-VFR to start Friday as a backdoor frontal
system works its way south into the region by Friday evening.
However locations across the north could see enough drying behind
the front to briefly return to VFR late Friday as the axis of
moisture drifts to the south. Locations across the southern part of
the CWA may also remain VFR through the period. Low level moisture
will then arc back north Friday night into Saturday, maintaining the
threat for additional sub- VFR in low cigs/fog, along with light
rain and/or drizzle, including possible patchy freezing rain across
the northern Blue Ridge. Unsettled weather will continue into Sunday
with some slow improvement in conditions as high pressure weakens to
the north leaving the residual weak front near the area. However
given uncertainty appears mainly MVFR to prevail under passing
showers as the boundary likely oscillates across parts of the
region. Southerly flow aloft will develop Monday ahead of a frontal
system in the Central Plains with continued MVFR as the low level
wedge redevelops while helping keep low clouds in place.
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